Traditional coal resource estimates have been conducted periodically in Kentucky for more than a century. Although these resource estimates suggest future mining potential on the order of hundreds of years, this potential may be greatly reduced if land-use and technological restrictions to mining are considered. "The Availability of Coal Resources for the Development of Coal" (also known as "Coal Availability") is a U.S. Geological Survey (USGS) program that is conducted cooperatively with state geological surveys. Its objectives are to characterize and quantify the kinds of factors that impede the development of coal in different regions of the country. These factors are broadly categorized as competing land uses (which arise from regulatory law) and technological constraints (engineering and geological impediments related to the mineability of the coal). The program was initially conducted in the Appalachian region, and has since expanded to the Eastern Interior and Western U.S. coal fields. Each study is conducted at a scale of 1:24,000 to include one or more 7.5-minute quadrangles.

The Kentucky Geological Survey has undertaken detailed studies of coal availability that take into account the effects of competing land uses and technological restrictions to mining on the remaining resource. Competing land uses may include state and national parks, municipal areas, cemeteries, and streams. Technological restrictions may include geologic and engineering constraints such as coal of insufficient thickness, unstable roof conditions, and proximity to adjoining underground mines. Results have been summarized in open-file reports and information circulars.

Eastern Kentucky
For eastern Kentucky, detailed coal-availability estimates have been prepared for nine 7.5-minute quadrangles in the region. The results for all studies show that technological restrictions are the most important factor in eastern Kentucky. Coal that is too thin to be mined by underground methods accounts for much of the restricted coal.

Western Kentucky
For western Kentucky, detailed estimates have been prepared for 14 quadrangles. These results also show that technological restrictions are the most important factor. In this region, a significant amount of one coal bed has been rendered unmineable because an underlying coal bed has been mined by underground methods. Also, several important coals have been extensively mined, and remaining coal is found at greater depths than has been mined in the past. Large areas of the Western Kentucky Coal Field contain alluvial valleys that may affect mineability of underlying coals. Although the valleys do not preclude mining, they add significantly to exploration and development costs.

Regional Studies: National Coal Assessment
In the course of preparing the quadrangle estimates, sampling bias was clear in the small study areas. In order to compensate for this effect, larger studies were prepared that ranged from 2 to 15 quadrangles. These analyses confirmed the general results of the earlier studies, but showed improved estimates for previous mining and further reduced the magnitude of land-use restrictions. The success of the larger studies led to a new program to assess coal resources on a basin-wide scale: the National Coal Assessment program .

Basin-wide Coal Availability Studies
The regional Coal Assessment maps make applying the Coal Availability methodology possible on a regional basis; consequently, the two programs are converging. Current Coal Availability studies are now done on a basin-wide scale.